Fuel pumps for internal combustion engines

ABSTRACT

A fuel injection pump includes a body in which is formed a bore. A two part plunger is located in the bore and the plunger is moved inwardly by means of a cam. The two parts of the plunger are separated by a space which during outward movement of the plunger under the action of a spring, is filled with fuel. During inward movement of the plunger, a port is initially closed by the outer plunger part, but before this occurs limited relative movement of the parts of the plunger takes place. The extent of such relative movement prior to the closure of the port determines the effective length of the plunger, and the instant at which fuel is supplied through an outlet to an associated engine.

Unite States atent [1 1 Fenne 1 Nov. 12, 1974 1 1 FUEL PUMPS FOR INTERNAL COMBUSTION ENGINES [75] Inventor: 1v0r Fenne, Greenford, England [73] Assignee: C.A.V. Limited, Birmingham,

England [22] Filed: Nov. 26, 1 973 {21] Appl. No.: 418,848

[52] US. Cl.... 417/293, 123/139 AM, 123/139 AF, 123/139 AC, 417/499, 417/494, 123/140 PG [51] Int. Cl F045 7/04, F02m 39/00 [58] Field of Search 417/494, 499, 293; 123/139 AM, 139 AF, 139 AC; 74/583 [56] References Cited UNITED STATES PATENTS 2,322,353 6/1943 Hohn 417/494 3.358.491 2/1958 Shook et al. 417/494 FOREIGN PATENTS OR APPLICATIONS 956,561 4/1964 Great Britain 123/139 AM Primary ExaminerCarlton R. Croyle Assistant Examiner-Richard E. Gluck Attorney, Agent, or Firml-1olman 8!. Stem [57] ABSTRACT A fuel injection pump includes a body in which is formed a bore. A two part plunger is located in the bore and the plunger is moved inwardly by means of a cam. The two parts of the plunger are separated by a space which during outward movement of the plunger under the action of a spring, is filled with fuel. During inward movement of the plunger, a port is initially closed by the outer plunger part, but before this occurs limited relative movement of the parts of the plunger takes place. The extent of suchrelative movement prior to the closure of the port determines the effective length of the plunger, and the instant at which fuel is supplied through an outlet to an associated engine.

7 Claims, 1 Drawing Figure FUEL PUMPS FOR INTERNAL COMBUSTION ENGINES This invention relates to fuel injection pumps for supplying fuel to internal combustion engines, the pump being of the kind comprising a body part, a bore defined in the body part, an outlet from one end of the bore, a plunger reciprocably mounted in the bore, cam means for imparting movement to the plunger in a di' rection inwardly towards said one end of the bore, a filling port formed in the wall of the bore, said filling port being covered by the end of the plunger during inward movement thereof, thereby to cause fuel to flow through said outlet and means for moving the plunger outwardly.

The object of the invention is to provide such a pump in a form in which the timing of delivery of fuel to the engine varies.

According to the invention, in a pump of the kind specified the plunger is divided into two parts, a space between said plunger parts being filled with liquid, the quantity of liquid varying in accordance with the speed at which the pump is driven so that the effective length of the plunger varies, and thereby the instant at which said port is closed by the plunger also varies.

According to a further feature of the invention, a further port is provided in the wall of the bore, said further port being uncovered to the space between the plunger parts so that said space is completely filled with liquid prior to the inward movement of the plunger, liquid being displaced out of said space through said further port until said further port is closed, the quantity of liquid remaining in said space determining the effective length of the plunger.

One example of a fuel injection pump in accordance with the invention will now be described with reference to the accompanying diagrammatic drawing.

Referring to the drawing, there is provided a body in which is formed a bore 11 one end of the bore is closed and is provided with an outlet 12 which through a conventional delivery valve 13 communicates with an injection nozzle (not shown) of an associated engine. Formed in the bore, but spaced from said one end thereof is a filling port 14 which communicates with a source 15 of liquid fuel at alow pressure.

Located within the bore is a plunger 16. The plunger is formed in two parts 16a, 16b, the two parts being interconnected by a linkage 17 such that the amount by which they can move away from each other is predetermined. In addition, a coiled compression spring 18 is interposed between the two parts of the plunger, and the parts are restrained by the linkage 17 against angular movement relative to each other.

The plunger 16 is movable inwardly by the action of a cam 23 which is driven in timed relationship with the engine, and is movable outwardly by means of a coiled compression spring 24. During inward movement, when the port 14 is covered by the end of the part 16a of the plunger, fuel will be delivered through the outlet 12 and past the delivery valve 13 to the engine. The amount of fuel which is supplied to the engine is determined by varying the angular position of the plunger with the bore and this is achieved using a rack bar 25 engaging a toothed portion 26 of the plunger. Conventional means establishing fluid communication between the top surface of part 16a and control edge 19 is provided. The effect of such angularmovement is to vary the instant during inward movement of the plunger at which the port 14 is uncovered by an inclined control edge 19 formed on the part 16a of the plunger.

Formed in the wall of the bore is a further port 20, and this communicates with a source of liquid conveniently the source 15 of fuel. As the port 20 is uncovered by the part 16b of the plunger doing its movement in an outward direction by means of the spring, fuel will flow into the space defined between the plunger parts, and in addition the plunger parts will be separated by the action of the spring 18. The extent of separation is determined by the means 17.

At the start of the inward movement of the plunger, the part 16]) thereof will move relative to the part i641. This is because the port 20 will be open, and in any case the part 16a has a considerable inertia. During relative movement of the two parts fuel will escape through the port 20. However, the quantity of fuel which will escape will be determined firstly by the size of the port 20, secondly by the speed of movement of the part 1617,

thirdly by the inertia of the part 1611, and fourthly by the pressure in said one end of the bore and which is acting upon the part 116a. In addition, of course, other factors such as the viscosity of the fuel will also have some bearing. It will be seen therefore that the part 16a of the plunger can start to move before the port 20 is closed. When the port 20 is closed, an hydraulic lock is created between the two parts of the plunger, which then move as a solid plunger towards said one end of the bore. Because the part 16a of the plunger can start to move before the port 20 is closed, it will be seen that the volume of the space defined between the plungers can vary, and so the effective length of the plunger varies so that the timing of the start of delivery of fuel through the outlet 12 also varies.

In the particular example, the spring R8 is provided because the fuel which is supplied to the port 20 has the same pressure as the pressure of fuel delivered by the source 15. In some instances, a separate source of fuel under pressure can be utilised to supply the port 20, and in this case, providing the pressure is higher than that of the source 15, the spring 18 may be omitted.

As shown in the drawing a control port 21 is provided adjacent said end of the bore, and this communicates with a non-return pressure control valve 22. The port 21 is arranged to, be covered by the end of the plunger part 16a before the port 14 is covered. The setting of the valve 22 may be utilised to control the pressure Within said end of the bore, and therefore the pressure acting upon the part 16a of the plunger.

I claim:

1. A fuel injection pump for supplying fuel to internal combustion engines, the pumpcomprising a body part in which is defined a bore, an outlet from one end of the bore, a plunger reciprocably mounted in the bore, cam means for imparting movement to the plunger in a direction inwardly towards said one end of the bore, a filling port formed in the wall of the bore, said filling port being covered by an end of the plunger during inward movement thereof thereby to cause fuel to flow through said outlet, means for moving the plunger in an instant at which said port is closed by the plunger also varies.

2. A pump as claimed in claim 1 including a further port provided in the wall of the bore, said further port being uncovered to the space between the plunger parts so that said space is completely filled with liquid prior to the inward movement of the plunger, liquid being displaced out of said space through said further port until said further port is closed, the quantity ofliquid remaining in said space determining the effective length of the plunger.

3. A pump as claimed in claim 2 including a valve operable to control the pressure in said one end of the bore prior to closure of the filling port by the plunger.

5. A pump as claimed in claim 3 in which said filling port and said further port communicate with a source of fuel under pressure there being interposed between the plunger parts a coiled compression spring.

6. A pump as claimed in claim 4 in which the part of the plunger at the inner end of the bore is provided with an inclined control edge which uncovers said filling port to terminate the delivery of fuel through the outlet, said part of the plunger being angularly adjustable to determine the quantity of fuel supplied through the outlet.

7. A pump, as claimed in claim 5, in which the part of the plunger at the inner end of the bore is provided with an inclined control edge, which uncovers said filling port to terminate the delivery of fuel through the outlet, said part of the plunger being angularly adjustable to determine the quantity of fuel supplied through the outlet. 

1. A fuel injection pump for supplying fuel to internal combustion engines, the pump comprising a body part in which is defined a bore, an outlet from one end of the bore, a plunger reciprocably mounted in the bore, cam means for imparting movement to the plunger in a direction inwardly towards said one end of the bore, a filling port formed in the wall of the bore, said filling port being covered by an end of the plunger during inward movement thereof thereby to cause fuel to flow through said outlet, means for moving the plunger in an outward direction, said plunger being divided into two parts, a space between said plunger partS being filled with liquid, the quantity of liquid varying in accordance with the speed at which the pump is driven so that the effective length of the plunger varies, and thereby the instant at which said port is closed by the plunger also varies.
 2. A pump as claimed in claim 1 including a further port provided in the wall of the bore, said further port being uncovered to the space between the plunger parts so that said space is completely filled with liquid prior to the inward movement of the plunger, liquid being displaced out of said space through said further port until said further port is closed, the quantity of liquid remaining in said space determining the effective length of the plunger.
 3. A pump as claimed in claim 2 including a valve operable to control the pressure in said one end of the bore prior to closure of the filling port by the plunger.
 4. A pump as claimed in claim 3 in which said filling port communicates with a source of fuel under pressure, said further port being adapted to communicate with a further source of fuel, having a pressure higher than that of the first mentioned source of fuel.
 5. A pump as claimed in claim 3 in which said filling port and said further port communicate with a source of fuel under pressure there being interposed between the plunger parts a coiled compression spring.
 6. A pump as claimed in claim 4 in which the part of the plunger at the inner end of the bore is provided with an inclined control edge which uncovers said filling port to terminate the delivery of fuel through the outlet, said part of the plunger being angularly adjustable to determine the quantity of fuel supplied through the outlet.
 7. A pump, as claimed in claim 5, in which the part of the plunger at the inner end of the bore is provided with an inclined control edge, which uncovers said filling port to terminate the delivery of fuel through the outlet, said part of the plunger being angularly adjustable to determine the quantity of fuel supplied through the outlet. 